Everything We Know About AMOC Collapse — And the Threat to North America's Coast

Summary

The video explains the Atlantic Meridional Overturning Circulation (AMOC), a large-scale Atlantic Ocean circulation that transports warm surface water northward and returns colder, denser water southward at depth. Heat released from the ocean helps moderate the climate in parts of Europe.

The AMOC is connected to, but not the same as, the Gulf Stream. The Gulf Stream is the fast, warm current along North America’s coast, driven largely by wind. AMOC discussions focus on the broader circulation, including the sinking of water in the North Atlantic.

What could weaken the AMOC?

The circulation depends partly on cold, salty water becoming dense enough to sink. Freshwater from Greenland ice melt and increased rainfall can make surface water less salty and less dense, potentially weakening that sinking.

The video describes a possible self-reinforcing process: weaker circulation carries less heat northward, which can reduce evaporation and salinity, further lowering water density. Whether the AMOC has a threshold beyond which it would shift into a persistently collapsed state—and how near it might be to such a threshold—remains unsettled.

Evidence of weakening

The video presents multiple lines of evidence that the AMOC is weakening, but says they do not establish a reliable collapse date.

• Direct measurements: The RAPID array has measured the circulation across the Atlantic at about 26.5°N since 2004. The video gives a best estimate of weakening by roughly 1 Sverdrup per decade, with a range of about 0.4–1.6. Natural variability is much larger than this trend, making it difficult to draw conclusions from a relatively short record.
• Ocean-temperature patterns: Researchers have identified a cold region south of Greenland and west of Ireland, along with other temperature patterns expected if less heat were transported northward. Historical observations provide a separate, indirect line of evidence.
• Seafloor sediment: Sediment grain size can indicate the speed of past deep-water currents. Reconstructions discussed in the video suggest that the AMOC is at its weakest in about a thousand years and that its decline began in the 20th century.

Estimates of a possible collapse

The video outlines the critical-slowing-down approach: as a system nears a tipping point, it may recover more slowly from disturbances.

Peter and Susanne Ditlevsen used this type of analysis in a 2023 study that estimated a possible collapse window of 2025–2095, with an average estimate of 2057. The video emphasizes that this date is disputed. The study relied on indirect temperature data, and critics raised concerns about the length and quality of the record, including a possible data gap. A model-based estimate should not be treated as a forecast.

Potential impacts

A full collapse could have different consequences on the two sides of the Atlantic:

• Climate models cited in the video show substantial cooling in parts of Europe under a complete-collapse scenario. These are model outcomes, not predictions.
• Along the North American Atlantic coast, a weaker current could reduce the effect that keeps sea surface levels lower near shore, contributing to higher regional sea levels. The video says coastal sea-level rise is already being measured and recommends consulting local projections.

Overall assessment

The video says the evidence for weakening is stronger than the evidence for a particular collapse date. The IPCC position described is that weakening this century is very likely, while a sudden collapse by 2100 is considered very unlikely, with medium confidence.

Longer direct measurements—potentially continuing into 2035–2040—could help distinguish a long-term trend from natural variability.

Methods and guidance highlighted

• Measure temperature, salinity, pressure, and flow using moored instruments across the Atlantic.
• Look for predicted temperature patterns in historical ocean observations.
• Use dated seafloor cores and sediment grain sizes to reconstruct past current speeds.
• Treat collapse dates cautiously. Ask whether a claim is based on direct measurements or models, and how long and reliable the underlying record is.
• For coastal planning, consult regional sea-level projections from NOAA in the United States and Fisheries and Oceans Canada.

Researchers and sources featured

Researchers

• Peter Ditlevsen — climatologist, University of Copenhagen
• Susanne Ditlevsen — statistician, University of Copenhagen
• Lewke Caesar
• Stefan Rahmstorf — Potsdam Institute
• René van Westen — Utrecht University
• Jasper Sverdrup — the Norwegian scientist after whom the Sverdrup unit is named

Institutions, programs, and publications

• RAPID monitoring program, a British-American project
• Intergovernmental Panel on Climate Change (IPCC)
• University of Copenhagen
• Potsdam Institute
• Utrecht University
• Nature — a study discussed in the video; its authors are not named in the subtitles
• National Oceanic and Atmospheric Administration (NOAA)
• Fisheries and Oceans Canada